<!DOCTYPE html>
<html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">
    <meta name="apple-mobile-web-app-capable" content="yes">
        <title>OpenLayers Cluster Strategy Threshold</title>
        <link rel="stylesheet" href="../theme/default/style.css" type="text/css">
        <link rel="stylesheet" href="style.css" type="text/css">
        <style type="text/css">
            ul {
                list-style: none;
                padding-left: 2em;
            }
            #reset {
                margin-left: 2em;
            }
        </style>
        <script src="../lib/OpenLayers.js"></script>
        <script type="text/javascript">

            // create a semi-random grid of features to be clustered
            var dx = 3;
            var dy = 3;
            var px, py;
            var features = [];
            for(var x=-45; x<=45; x+=dx) {
                for(var y=-22.5; y<=22.5; y+=dy) {
                    px = x + (2 * dx * (Math.random() - 0.5));
                    py = y + (2 * dy * (Math.random() - 0.5));
                    features.push(new OpenLayers.Feature.Vector(
                        new OpenLayers.Geometry.Point(px, py), {x: px, y: py}
                    ));
                }
            }

            var map, strategy, clusters;
            function init() {
                map = new OpenLayers.Map('map');
                var base = new OpenLayers.Layer.WMS("OpenLayers WMS", 
                    ["http://t3.tilecache.osgeo.org/wms-c/Basic.py",
                     "http://t2.tilecache.osgeo.org/wms-c/Basic.py",
                     "http://t1.tilecache.osgeo.org/wms-c/Basic.py"], 
                    {layers: 'satellite'}
                );

                var style = new OpenLayers.Style({
                    pointRadius: "${radius}",
                    fillColor: "#ffcc66",
                    fillOpacity: 0.8,
                    strokeColor: "#cc6633",
                    strokeWidth: "${width}",
                    strokeOpacity: 0.8
                }, {
                    context: {
                        width: function(feature) {
                            return (feature.cluster) ? 2 : 1;
                        },
                        radius: function(feature) {
                            var pix = 2;
                            if(feature.cluster) {
                                pix = Math.min(feature.attributes.count, 7) + 2;
                            }
                            return pix;
                        }
                    }
                });
                
                strategy = new OpenLayers.Strategy.Cluster();

                clusters = new OpenLayers.Layer.Vector("Clusters", {
                    strategies: [strategy],
                    styleMap: new OpenLayers.StyleMap({
                        "default": style,
                        "select": {
                            fillColor: "#8aeeef",
                            strokeColor: "#32a8a9"
                        }
                    })
                });
                
                var select = new OpenLayers.Control.SelectFeature(
                    clusters, {hover: true}
                );
                map.addControl(select);
                select.activate();
                clusters.events.on({"featureselected": display});

                map.addLayers([base, clusters]);
                map.setCenter(new OpenLayers.LonLat(0, 0), 2);
                
                reset();
                $("reset").onclick = reset;

            }
            
            function reset() {
                var distance = parseInt($("distance").value);
                var threshold = parseInt($("threshold").value);
                strategy.distance = distance || strategy.distance;
                strategy.threshold = threshold || strategy.threshold;
                $("distance").value = strategy.distance;
                $("threshold").value = strategy.threshold || "null";
                clusters.removeFeatures(clusters.features);
                clusters.addFeatures(features);
            }
            
            function display(event) {
                var f = event.feature;
                var el = $("output");
                if(f.cluster) {
                    el.innerHTML = "cluster of " + f.attributes.count;
                } else {
                    el.innerHTML = "unclustered " + f.geometry;
                }
            }
            
            
        </script>
    </head>
    <body onload="init()">
        <h1 id="title">Cluster Strategy Threshold</h1>
        <div id="tags">
            vector, feature, stylemap, wfs, cluster, strategy, cleanup
        </div>         
        <p id="shortdesc">
            Demonstrates the use of the cluster strategy threshold property.
        </p>
        <div id="map" class="smallmap"></div>
        <div id="docs">
            <p>The Cluster strategy lets you display points representing clusters
            of features within some pixel distance.  You can control the behavior
            of the cluster strategy by setting its distance and threshold properties.
            The distance determines the search radius (in pixels) for features to
            cluster.  The threshold determines the minimum number of features to
            be considered a cluster.</p>
        </div>
        <br>
        <p>Cluster details: <span id="output">hover over a feature to see details.</span></p>
        <ul>
            <li>
                <input id="distance" name="distance" type="text" value="" size="3" />
                <label for="distance">distance</label>
            </li>
            <li>
                <input id="threshold" name="threshold" type="text" value="" size="3" />
                <label for="threshold">threshold</label>
            </li>
        </ul>
        <button id="reset">recluster</button>
    </body>
</html>
